As an exhaust gas purification catalyst provided in an exhaust passage of an internal combustion engine, there has been developed heretofore an electric heating catalyst (which will be hereinafter referred to as “EHC”), in which a catalyst is heated by a heater element that generates heat by supply of electric current.
The EHC has a heater element that generates heat by supply of electric power, a casing that houses the heater element, and an insulation member for electrical insulation provided between the heater element and the casing. For example, Patent Document 1 discloses a technique of providing a mat made of an insulating material between a carrier that generates heat by supply of electric current and a casing that houses the substrate. By using such an insulation member, short circuit between the heater element and the casing can be prevented.